Illumination of covered areas of buildings by other than interior light sources has a long history. Initially, openings were made in roofs over the areas. While the openings did provide light, and incidental ventilation, such openings also allowed the entrance of rain and snow. Early on, it was learned that the mere covering of such openings with at least a translucent material would keep rain and snow from falling through the opening. However, it was also learned that rain flowing down a roof could seep under the opening cover. To offset this, openings were built with a wall around the opening and the opening cover was placed on such a wall. While the wall around the opening did stop the flow of water directly into the opening, it was recognized that it was necessary to seal the juncture of the wall and the opening in the roof. The openings were normally made between the roof rafters or trusses so as not to lessen or weaken the supports for the roof. Generally, the wall of opening in the roof had a sealant of a mastic or metal flashing plates which underlay the final roof covering. Application of such sealants was time consuming. The mastic sealants were subject to dehydration and resultant withdrawal from contact between the opening wall and the roof. The use of flashing materials, which primarily are metal flanges, requires that the horizontal portion of the flange be secured to the basic roof surface and the vertical portion of the flashing be secured to the vertical surface of the wall. Once this sealing had been made, it then was required that the at least translucent covering of the opening be sealingly secured to the curb to prevent the influx of moisture during a heavy rainfall which could overflow the opening cover and on the opposite aspect allow the outward flow of interior heated air. Additionally in climatic areas subject to cold temperature, the humidity within the covered space normally results in the formation of moisture on the interior surface of the opening covering even though the covering may be double glazed.
Currently, the coverings for openings in roofs to provide light are referred to as skylights. Such skylights are characterized as rectilinear boxes having a double glazed covering. Such boxes are secured by insertion between the roof rafters or trusses by conventional means as nails, screws and the like. Waterproofing is normally accomplished by the use of stepped flashing, i.e., L-shaped metal sheets secured to the skylight frame, beginning at the lower end of the skylight insertion. After such flashing is completed, the final roof covering, shingles or tiles are installed. Such sealing of the skylight unit insertion is time consuming, and due to the nature of the sealants to dry out and retract, can require constant monitoring and repairs. To remove condensation from the interior surface of the innermost glazing, it is common practice to drill small weep holes in the vertical wall of the lower end of the skylight to allow the collected condensation to flow out onto the roof surface. The presence of such weep holes also allows air flow from the interior of the building.